Antenna tuned by bending end portions



y 1963 H. ODENWALD 3,089,141

ANTENNA TUNED BY BENDING END PORTIONS Filed June 10, 1955 Inventor.-

Unite States The invention relates to a new aerial system for thereception of very high frequency signals, particularly televisionsignals, which is also suitable for the propagation of high frequencyenergy from a transmitter.

It is an object of this invention to provide an aerial system foroutdoor use which is easily tunable within predetermined limits offrequency or to predetermined channels, even after the aerial has beencompletely installed.

A further object of the invention is to provide means for tuning anaerial, which are mechanically simple and inexpensive, but at the sametime completely resistant to weather and strong enough for outdoor use.

Another and very important object of the invention is to provide meanswhich do not only allow to increase the resonance frequency, but also toreturn to a lower resonance frequency, i.e. according to this inventionreversible tuning of the aerial system in both directions withinpredetermined limits of frequency is possible.

A further object of the invention is to provide an aerial system havingthe above mentioned objects in which the frequencies or channels, towhich the aerial can be tuned, are indicated preferably by engraving orpunching in the tuning means.

It is common practice to provide tunable aerials, for example, indooraerials, wherein the aerial elements can be pulled out and pushed backin the manner of a tele scope. However, this type of aerial isexpensive, not sufficiently resistant to weather, and not strong enoughfor outdoor use.

Moreover, it is known to make extensible dipole antennas from two rodswherein the ends of the rods contain a plurality of notches for thepurpose of tuning the dipole to a higher frequency by electricallycutting off the ends. However, it is considered a serious drawback withthese antennas that the resonance frequency can only be shifted tohigher frequencies and the change cannot be made retrogressive.

With the aerial of the present invention, on the contrary, it ispossible to effect such reversible tuning, within certain limits, inboth directions. In addition, the aerial is very simple, inexpensive andcompletely weather resistant.

The length of the aerial elements, according to the present invention,is also changed for tuning purposes. This is made possible by providingclose to the dipole ends one or more elements capable of being bent,which are more resilient than the antenna elements themselves, due to asuitable deviation either in the form and/ or in the material employed,and which may be bent repeatedly back and forth, without breaking off.Such elements capable of bending are known per se. They are used, forexample, in connection with aerials used on vehicles and are mountedclose to the base of the aerial so as to permit adapting the inclinationof the aerial, in a simple way, to the contours of the vehicle body.Moreover, it has been proposed to use a device consisting of two metalbands lying in the same plane and having comb-like slits, for connectinga source of high frequency with a mismatched receiving set. In order toimprove the adaptation of the device it was proposed to bend the flapsformed by the slits inwardly about 90 so that their surfaces extendparallel and at a relatively short atet O ice distance from each other,thus forming a transverse capaoity which, when applied at a suitablepoint, produces a reduction of the stationary waves upon said device.

Such prior use of bending elements was not suggestive of the aerials ofthe present invention which were based up an entirely different concept.

The aerial system according to the present invention comprises at leastone, but in most cases of practical use several stretched or rod-likeelements, which may be approximately as long as half of the operatingwave length or as long as the whole operating wave length. For purposeof tuning the length of the said aerial-elements is changed. This ismade possible by providing close to the extreme free ends of the saidelements at least one section capable of being bent, which is moreyielding with respect to nonresilient deformation than the said aerialelements themselves, so that the said extreme ends can be bent easilyforward and back several times without breaking off and will remain inany bent position.

The said bending sections can be made of a metal having a lower yieldpoint (flow limit) than the material of the said aerial elementsthemselves, and/ or they may be shaped in such a way that they have asmaller section modulus (resistance moment) than the said aerial elementthemselves. For this purpose they can have a different form or size ofcross-section.

The aerial elements inclusive the bending sections may consist of arelatively hard material, only said bending sections being annealed.Alternatively, the aerial elements may be originally soft andsubsequently hardened all over with exception of the said bendingsections.

The invention will be better understood from the following descriptionwhen considered in connection with the accompanying drawings and itsscope will be pointed out in the appended claims.

A typical example of an element of the aerial according to the presentinvention is shown in FIG. 1 in the original shape.

FIG. 2 and FIG. 3 shows the same aerial element, the bending sectionsbeing bent by and respectively.

FIG. 4 shows a further embodiment of an element of the aerial accordingto the present invention which has however several bending sections onthe free ends.

An element of the aerial according to the present invention is shown, byway of example, in FIG. 1. It consists of an insulated carrier 1,adapted to receive a feed cable or other type of transmission line, andwhich may be associated laterally with two metal rods or pipes (2 and 3)which together form an extended open dipole. This dipole can beapproximately as long as one-half or one whole wave length of itsoperational frequency. At the transition point leading to the extremeends 4 and 5 of the metal rods or pipes, there are provided bendingsections 6 and 7 which, due to either their form and/or the metal ofwhich they are made, are more yielding with respect to non-resilientdeformation than the aerial rods or pipes themselves. Thus, it ispossible to even subsequently bend the ends of the mounted aerial, withthe greatest ease, for example, to the extent of 90 as shown in FIG. 2,or to the extent of 180 as shown in FIG. 3. In this way the electricallyuseful length of the aerial element can be constantly varied between twolimits.

The bending sections can be made of a metal having a lower flow limitthan the material of the aerial element itself, and/or they may beshaped in such a way that their resistance moment is smaller than theaerial element itself. The bending sections may be pieces obtained bysoft annealing of an otherwise rigid rod or pipe. The aerial rods orpipes may, on the other hand, be soft to begin with and then hardenedwith the exception of the bending points.

FIG. 4 shows a further embodiment of an element of the aerial accordingto the invention. It consists, like the element according to FIG. 1, ofthe insulated portion 1 with two associated rods or pipes 2 and 3.However, at the ends of the latter there are provided in this case aplurality of bending sections 8 to 11 alternating with more rigid rod orpipe sections 12 to 15. It is, of course, possible to increase thisnumber as desired. An aerial, consisting of such elements, can beselectively tuned to several definite frequencies or, for example,television channels, by bending over one or more segments 12, 13, 14, 15at the points defined by the bending sections, to the positionillustrated in FIG. 3. The frequencies and the channel numbers aresuitably indicated on each of the segments, preferably by engraving orpunching.

It is possible to assemble multiple element aerials from such elementsin any desired order. In this connection, the elements of a multipleelement aerial may all or only in part be tunable.

In the case of parasitic elements (reflectors and directors), theinsulating portion 1 can be left out, if it is not needed. The scope ofthe invention is to include all aerials constructed according to theinvention, regardless of their use for receiving or transmittingpurposes of all kinds. The illustrated form of a symmetrical dipole isonly given by way of example. Other types of aerials, for exampleunsymmetrical rod aerial (Marconi aerial) which can be tuned in themanner of the present invention, are also within the contemplated scope.

It is, of course, immaterial for the purpose of the present invention,Whether or not ends 4 and 5 extending from bending sections 6 and 7(HG. 1) be made of the same material and possess the samecross-sectional form, i.e. the same diameter, as the aerial rods 2 and3. They may, on the contrary, consist of any conducting material andhave any desired cross-sectional form. "They may consist, for example,of the same material and have the same diameter as the bending elements.

I claim:

1. A tunable aerial for outdoor use, comprising at least one rod-likeelement consisting of a non-elastic intermediate portion and bendablesections at the extreme free ends of said intermediate portion, having alength which is only a small fraction of the length of said intermediateportion and serving as means for reversible tuning of the aerial withinpredetermined limits of frequency, said bendable sections at least attheir portions in the neighborhood of the said non-elastic intermediateportion offering less resistance to bending than the said non-elasticintermediate portion, so that said bendable sections can be bent easilybackward and forward through an angle up to 180 several times withoutbreaking off and will remain in any bent position.

2. A tunable aerial for outdoor use, comprising at least one rod-likeelement consisting of a non-elastic intermediate portion and bendablesections at the extreme :free ends of said intermediate portion, havinga length which is only a small fraction of the length of saidintermediate portion and serving as means for reversible tuning of theaerial within predetermined limits of frequency, said bendable sectionsat least at their portions :in the neighborhood of the said non-elasticintermediate portion consisting of a more flexible material than thesaid non-elastic intermediate portion, so that said bendable sectionscan be bent easily backward and forward through an angle up to 180several times without breaking oil? and will remain in any bentposition.

3. A tunable aerial for outdoor use, comprising at least one rod-likeelement consisting of a non-elastic intermediate portion and bendablesections at the extreme free ends of said intermediate portion, having alength which is only a small fraction of the length of said intermediateportion and serving as means for reversible tuning of the aerial withinpredetermined limits of frequency, said bendable sections at least attheir portions in the neighborhood of the said non-elastic intermediateportion being more flexible due to the different form of cross-sectionthan the non-elastic intermediate portion, so that said bendablesections can be bent easily backward and forward through an angle up toseveral times without breaking off and will remain in any bent position.

4. A tunable aerial for outdoor use, comprising at least one rod-likeelement consisting of a non-elastic intermediate portion and bendablesections at the extreme free ends of said intermediate portion, having alength which is only a small fraction of the length of said intermediateportion and serving as means for reversible tuning of the aerial withinpredetermined limits or" frequency, said bendable sections at least attheir portions in the neighborhood of the said non-elastic intermediateportion being more flexible due to the different size of cross-sectionthan the non-elastic intermediate portion, so that said bendablesections can be bent easily backward and forward through an angle up to180 several times without breaking off and will remain in any bentposition.

5. A tunable aerial for outdoor use, comprising at least one rod-likeelement consisting of a non-elastic intermediate portion and bendablesections at the extreme free ends of said intermediate portion, having alength which is only a small fraction of the length of said intermediateportion and serving as means for reversible tuning of the aerial withinpredetermined limits of frequency, said aerial elements including saidbending sections being made of a relatively hard metal and only saidbending sections being annealed, so that said bendable sections can bebent easily backward and forward through an angle up to 181? severaltimes without breaking off and will remain in any bent position.

6. A tunable aerial for outdoor use, comprising at least one rod-likeelement consisting of a non-elastic intermediate portion and bendablesections at the extreme free ends of said intermediate portion, having alength which is only a small fraction of the length of said intermediateportion and serving as means for reversible tuning of the aerial withinpredetermined limits of frequency, said aerial elements including saidbending sections being made of a soft metal and hardened with exceptionof the bendable sections, so that said bendable sections can be benteasily backward and forward through an angle up to 180 several timeswithout breaking off and will remain in any bent position.

7. A tunable aerial for outdoor use, comprising at least one rod-likeelement consisting of a non-elastic intermediate portion and a pluralityof bendable sections at certain intervals at the extreme free ends ofsaid intermediate portion, having a length which is only a smallfraction of the length of said intermediate portion and serving as meansfor reversible tuning of the aerial within predetermined limits offrequency, said bendable sections at least at their portions in theneighborhood of the said non-elastic intermediate portion, respectivelyin the neighborhood of the outer ends of the other bendable sections,offering less resistance to bending than the said nonelasticintermediate portion, so that said bendable sections can be bent easilybackward and forward through an angle up to 180 several times withoutbreaking off and will remain in any bent position.

8. A tunable aerial for outdoor use, comprising at least one rod-likeelement consisting of a non-elastic intermediate portion and a pluralityof bendable sections at certain intervals at the extreme free ends ofsaid intermediate portion, having a length which is only a smallfraction of the length of said intermediate portion and serving as meansfor reversible tuning of the aerial within predetermined limits offrequency, these frequencies or number of channels being indicated onthe said References Cited in the file of this patent UNITED STATESPATENTS Morrison June 4, 1929 Schwarzhaupt Jan. 26, 1935 6 Gordon Mar.5, 1940 Harsted July 3, 1945 Bigue Apr. 22, 1947 Spindler Dec. 27, 1949Lidz Aug. 28, 1951 Albright June 16, 1953 Smeby July 28, 1953 Kleis Oct.27, 1953

1. A TUNABLE AERIAL FOR OUTDOOR USE, COMPRISING AT LEAST ONE ROD-LIKEELEMENT CONSISTING OF A NON-ELASTIC INTERMEDIATE PORTION AND BENDABLESECTIONS AT THE EXTREME FREE ENDS OF SAID INTERMEDIATE PORTION, HAVING ALENGTH WHICH IS ONLY A SMALL FRACTION OF THE LENGTH OF SAID INTERMEDIATEPORTION AND SERVING AS MEANS FOR REVERSIBLE TUNING OF THE AERIAL WITHINPREDETERMINED LIMITS OF FREQUENCY, SAID BENDABLE SECTIONS AT LEAST ATTHEIR PORTIONS IN THE NEIGHBORHOOD OF THE SAID NON-ELASTIC INTERMEDIATEPORTION OFFERING LESS RESISTANCE TO BENDING THAN THE SAID NON-ELASTICINTERMEDIATE PORTION, SO THAT SAID BENDABLE SECTIONS CAN BE BENT EASILYBACKWARD AND FORWARD THROUGH AN ANGLE UP TO 180* SEVERAL TIMES WITHOUTBREAKING OFF AND WILL REMAIN IN ANY BENT POSITION.